Registration of the First Thermonuclear X-ray Burst from AX J1754.2-2754

During the analysis of the INTEGRAL observatory archival data we found a powerful X-ray burst, registered by JEM-X and IBIS/ISGRI telescopes on April 16, 2005 from a weak and poorly known source AX J1754.2-2754. Analysis of the burst profiles and spectrum shows, that it was a type I burst, which result from thermonuclear explosion on the surface of nutron star. It means that we can consider AX J1754.2-2754 as an X-ray burster. Certain features of burst profile at its initial stage witness of a radiation presure driven strong expansion and a corresponding cooling of the nutron star photosphere. Assuming, that the luminosity of the source at this phase was close to the Eddington limit, we estimated the distance to the burst source d=6.6+/-0.3 kpc (for hidrogen atmosphere of the neutron star) and d=9.2+/-0.4 kpc (for helium atmosphere).Comment: 12 pages, 6 figure

Outburst of the X-ray transient SAX J1818.6-1703 detected by INTEGRAL in September 2003

During the observation of the Galactic-center field by the INTEGRAL observatory on September 9, 2003, the IBIS/ISGRI gamma-ray telescope detected a short (several-hours-long) intense (~380 mCrab at the peak) outburst of hard radiation from the X-ray transient SAX J1818.6-1703. Previously, this source was observed only once in 1998 during a similar short outburst. We present the results of our localization, spectral and timing analyses of the object and briefly discuss the possible causes of the outburst. The release time of the bulk of the energy in such an outburst is appreciably shorter than the accretion (viscous) time that characterizes the flow of matter through a standard accretion disk.Comment: 16 pages, 7 figures, to be published in Astronomy Letters, v. 31, n. 10, p. 672 (2005

INTEGRAL observations of five sources in the Galactic Center region

A number of new X-ray sources (IGR J17091-3624, IGR/XTE J17391-3021, IGR J17464-3213 (= XTE J17464-3213 = H 1743-322), IGR J17597-2201, SAX/IGR J18027-2017) have been observed with the INTEGRAL observatory during ultra deep exposure of the Galactic Center region in August-September 2003. Most of them were permanently visible by the INTEGRAL at energies higher than $\sim 20$ keV, but IGR/XTE J17391-3021 was observed only during its flaring activity with a flux maximum of $\sim120$ mCrab. IGR J17091-3624, IGR J17464-3213 and IGR J17597-2201 were detected up to $\sim 100$-150 keV. In this paper we present the analysis of INTEGRAL observations of these sources to determine the nature of these objects. We conclude that all of them have a galactic origin. Two sources are black hole candidates (IGR J17091-3624 and IGR J17464-3213), one is an LMXB neutron star binary (presumably an X-ray burster) and two other sources (IGR J17597-2201 and SAX/IGR J18027-2017) are neutron stars in high mass binaries; one of them (SAX/IGR J18027-2017) is an accreting X-ray pulsar.Comment: 8 pages, 7 figures, 2 tables, accepted for publication in A&

Regenerating Nucleus Pulposus of the Intervertebral Disc Using Biodegradable Nanofibrous Polymer Scaffolds

Low back pain is a leading health problem in the United States, which is most often resulted from nucleus pulposus (NP) degeneration. To date, the replacement of degenerated NP relies entirely on mechanical devices. However, a biological NP replacement implant is more desirable. Here, we report the regeneration of NP tissue using a biodegradable nanofibrous (NF) scaffold. Rabbit NP cells were seeded on the NF scaffolds to regenerate NP-like tissue both in vitro and in a subcutaneous implantation model. The NP cells on the NF scaffolds proliferated faster than those on control solid-walled (SW) scaffolds in vitro. Significantly more extracellular matrix (ECM) production (glycosaminoglycan and type II collagen) was found on the NF scaffolds than on the control SW scaffolds. The constructs were then implanted in the caudal spine of athymic rats for up to 12 weeks. The tissue-engineered NP could survive, produce functional ECM, remain in place, and maintain the disc height, which is similar to the native NP tissue.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98480/1/ten%2Etea%2E2011%2E0747.pd

Broadband X-ray spectrum of XTE J1550-564 during 2003 outburst

Results of broadband INTEGRAL and RXTE observations of the Galactic microquasar XTE J1550-564 during outburst in spring 2003 are presented. During the outburst the source was found in a canonical low/hard spectral state.Comment: 5 pages, 3 figures. Accepted for publication in Astronomy Letter

New fast X-ray transient IGR J18462-0223 discovered by the INTEGRAL observatory

Details of the discovery of a new X-ray source, IGR J18462-0223, on October 12, 2007, during a short (several hours), intense (~ 35 mCrab at the peak) outburst of hard radiation by the IBIS/ISGRI gamma-ray telescope onboard the INTEGRAL observatory are given. The detection of another earlier outburst from this source occurred on April 28, 2006, in the archival data of the telescope is reported. We present the results of the source's localization and our spectral/timing analysis of the observational data. The source may turn out to be yet another representative of the continuously growing population of fast X-ray transients, which are the focus of attention because of the identification of their optical counterparts with early-type supergiants